Method for preparing titanium carbonitride from titanium-containing blast furnace slag

Abstract

The application discloses a method for preparing titanium carbonitride from titanium-containing blast furnace slag. The method comprises the following steps: firstly, using a three-phase alternating current closed furnace to smelt the titanium-containing blast furnace slag by adding carbon, so that TiO2 in the slag is converted into low-valence titanium; and secondly, using nitrogen as a carrier gas of the carbonaceous reducing agent to perform a counter-blowing wind quenching on the obtained molten slag containing low-valence titanium, so as to obtain titanium carbonitride particles. The method can effectively solve the problems existing in smelting titanium-containing blast furnace slag to extract titanium resources in a carbonization furnace, and by changing a smelting process, utilizing the condition that titanium carbide and titanium carbonitride have similar physical and chemical characteristics, taking Ti(C,N) as a replacement product of TiC, matching a wind quenching and slagging process corresponding to the process, smelting power consumption can be significantly reduced, product quality can be further improved, parameter control in a lower process can be more favorable, product yield can be improved, and economic benefits are very obvious.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical and chemical technology, specifically relating to a method for preparing titanium carbonitride from titanium-containing blast furnace slag. Background Technology

[0002] Titanium magnetite concentrate is mainly used for blast furnace ironmaking. After smelting, titanium, in the form of TiO2, almost entirely enters the high-titanium blast furnace slag, accounting for approximately 20% to 28%, making it the largest titanium-containing resource in terms of total amount. For a long time, no practical method has been found to recover and utilize the titanium resources in blast furnace slag. Titanium in titanium-containing blast furnace slag is distributed in multiple mineral phases, with a small particle size averaging around 10 μm. For this dispersed and fine ore, traditional beneficiation methods are insufficient to separate TiO2. Currently, the main titanium extraction process is the acid leaching, alkali fusion, and hydrolysis wet process. Because TiO2 is difficult to concentrate and has a low grade, the titanium-containing blast furnace slag needs to be completely ground before leaching, resulting in high acid and alkali consumption, complex process flow, high cost, large amounts of difficult-to-treat waste, and new pollution.

[0003] High-temperature carbonization utilizes the electric furnace slag melting and reduction carbonization to produce carbonized slag, with a TiC content reaching 10%–16%. Through continuous process practice and exploration, a relatively mature smelting mode has been achieved. However, there are still some key problems in producing carbonized slag using the melting and reduction carbonization of titanium-containing blast furnace slag, such as high melting and reduction carbonization temperature, long cycle, and high power consumption; severe coke floating during the smelting and carbonization process; and the fine TiC particle size of the carbonized TiC, only a few to a dozen micrometers, resulting in solid-liquid coexistence in the molten pool, increased slag-liquid viscosity, and reduced surface tension. This makes it easy for the gas generated during the process to float to the surface, creating conditions for foaming and easily producing foamy slag. In addition, the TiC grade produced by traditional carbonization processes is low, resulting in poor product quality and impacting economic efficiency. In the smelting process of preparing carbide slag by using carbonaceous reducing agent and titanium-containing blast furnace slag, the reaction process follows thermodynamic laws. TiO2 in the slag first produces low-valent titanium at low temperature (1100℃~1300℃). As the temperature of the molten pool continues to increase, when it reaches above 1300℃, the low-valent titanium continues to react with the carbonaceous reducing agent to generate TiC, thus realizing the entire process of preparing carbide slag. In the second stage of the reaction, it is necessary to continuously replenish energy in the molten pool to ensure that the reaction process proceeds in the forward direction. Summary of the Invention

[0004] To overcome the aforementioned deficiencies in existing technologies, the present invention aims to provide a new high-efficiency in-furnace smelting mode and proposes a solution for preparing titanium carbonitride (Ti(C,N)) from titanium-containing blast furnace slag. This solution can further reduce smelting power consumption and production costs, improve production efficiency, and optimize product quality. In turn, it solves the problems of long reaction time, high smelting power consumption, uneven particle size of water-quenched titanium carbide slag, and low TiC grade in traditional processes.

[0005] To achieve the above-mentioned objective, the present invention provides a method for preparing titanium carbonitride from titanium-containing blast furnace slag, the method comprising the following steps:

[0006] ① Use a three-phase AC closed electric furnace with carbon to smelt titanium-containing blast furnace slag, so that TiO2 in the slag is converted into low-valent titanium;

[0007] Titanium carbide and titanium carbonitride have similar physicochemical properties, therefore Ti(C,N) can be used as a substitute for TiC. The energy consumed in the conversion of TiO2 to low-valent titanium is significantly lower than that in the conversion of TiO2 to Ti(C,N), and the reaction time is also shorter. According to the thermodynamic equation 2Ti2O3 + 10C + 2N2 = 4TiNC + 6CO, the initial reaction temperature is approximately 1473K, and the reaction rate increases with increasing temperature. Using a three-phase AC closed electric furnace with carbon, titanium-containing blast furnace slag can be smelted. By controlling the reaction temperature and the ratio of carbonaceous reducing agent, TiO2 in the slag can be converted into low-valent titanium such as Ti2O3 or Ti3O5.

[0008] In the above technical solution, the smelting temperature of the three-phase AC closed electric furnace is further controlled at 1100℃~1500℃, the slag discharge temperature is 1300℃~1700℃, and the smelting time is 45~60min.

[0009] Furthermore, the carbonaceous reducing agent is formulated at 3.5%–4.5% of the mass of the titanium-containing blast furnace slag. A high slag discharge temperature is beneficial for increasing the conversion rate of low-valent titanium such as Ti₂O₃ or Ti₃O₅ to Ti(C,N) during air quenching and spraying, while simultaneously ensuring that the particle size of the carbonaceous reducing agent during smelting is 1–5 mm and the carbon content is fixed at ≥75%.

[0010] ②Using nitrogen as a carrier gas to perform counter-current blowing quenching on the slag containing low-valent titanium obtained in step ①, titanium carbonitride particles are obtained.

[0011] Furthermore, the nitrogen pressure is controlled at 0.4–0.7 MPa, the nitrogen flow rate is controlled at 90–120 m / s, and the nitrogen flow rate is determined by the amount of molten slag discharged. During air quenching, the carbonaceous reducing agent ratio is 9%–11% of the mass of the titanium-containing blast furnace slag, with a particle size of 75–200 μm and a fixed carbon content ≥90%. During the slag discharge process, the slag flow is large in the early stage and small in the later stage. By adjusting the nitrogen flow rate, it is ensured that the Ti(C,N)-containing hot molten slag forms uniformly sized particles with a particle size distribution of 1–2 mm. During air quenching, since nitrogen is a protective gas used for oxidation prevention, it can ensure a non-oxidizing environment, which helps stabilize the grade of titanium carbonitride. Adjusting the nitrogen flow rate by the amount of slag discharged ensures particle uniformity and is more conducive to parameter control in subsequent processes.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] This invention divides the preparation of titanium carbonitride from titanium-containing blast furnace slag by carbothermic reduction of TiO2 into three stages: TiO2 → Ti n O 2n -1 (reduction speed is relatively fast in this stage), Ti n O 2n -1→TiC x N z O y (The gasification reaction of carbon plays a key role in this stage), and the introduction of N2 can lower the reduction temperature, leading to the next stage: TiC. x N z O y →Ti(C, N). This invention reduces the second stage of directly reducing TiO2 in titanium-containing blast furnace slag with a reducing agent: the process of producing TiC from low-cost titanium, thus reducing the continuous energy supply and reaction time in the process.

[0014] This invention effectively solves the problem of extracting titanium resources from titanium-containing blast furnace slag in carbide furnaces. By changing the smelting process and utilizing the similar physicochemical properties of titanium carbide and titanium carbonitride, Ti(C,N) is used as a replacement product for TiC. Combined with a wind quenching slag removal process that is compatible with the process, the smelting power consumption can be significantly reduced and the product quality can be further improved. It is also more conducive to the parameter control of subsequent processes and the improvement of product yield, resulting in significant economic benefits. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the main process equipment flow of a method for preparing titanium carbonitride from titanium-containing blast furnace slag according to the present invention;

[0016] Figure 2 Image of the titanium carbonitride sample prepared in Example 1. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but this does not limit the invention in any way. To avoid redundancy, unless otherwise specified, the raw materials used in the following embodiments are all commercially available products, and the methods used are all conventional methods unless otherwise specified.

[0018] A method for preparing titanium carbonitride from titanium-containing blast furnace slag, the main process flow is as follows: Figure 1 As shown, the specific steps include the following:

[0019] ① Use a three-phase AC closed electric furnace with carbon to smelt titanium-containing blast furnace slag, so that TiO2 in the slag is converted into low-valent titanium;

[0020] ②Using nitrogen as a carrier gas to perform counter-current blowing quenching on the slag containing low-valent titanium obtained in step ①, titanium carbonitride particles are obtained.

[0021] Any aspects not described in the following embodiments are the same as those described in the specific embodiments above.

[0022] Example 1

[0023] A method for preparing titanium carbonitride from titanium-containing blast furnace slag includes the following steps:

[0024] ① A three-phase AC closed electric furnace is used to smelt titanium-containing blast furnace slag with carbon, so that TiO2 in the slag is converted into low-valence titanium; the smelting temperature of the three-phase AC closed electric furnace is controlled at 1380℃, the slag discharge temperature is 1550℃, and the smelting time is 60min.

[0025] The carbonaceous reducing agent is formulated at 3.5% of the mass of titanium-containing blast furnace slag, with a particle size of 1–5 mm and a fixed carbon content of 79%.

[0026] ② Using nitrogen as the carrier gas for carbonaceous reducing agent, the slag containing low-valent titanium obtained in step ① is subjected to counter-current blowing and air quenching to obtain titanium carbonitride particles. The nitrogen pressure is controlled at 0.4 MPa, and the nitrogen flow rate is controlled at 90 m / s. During air quenching, the carbonaceous reducing agent ratio is 9% of the mass of the titanium-containing blast furnace slag, with a particle size of 75 μm and a fixed carbon content of 92%. By adjusting the nitrogen flow rate, the hot molten slag containing Ti(C,N) is ensured to form uniformly sized particles with a particle size distribution of 1–2 mm.

[0027] The titanium carbonitride obtained in Example 1 had a grade of 13.82% (sample as shown). Figure 2 As shown in the figure, the reaction time was shortened by 23 minutes and the smelting power consumption was reduced by 14.32%; the water-quenched slag particles were uniform, with 95% being 1-2 mm.

[0028] Example 2

[0029] A method for preparing titanium carbonitride from titanium-containing blast furnace slag includes the following steps:

[0030] ① A three-phase AC closed electric furnace is used to smelt titanium-containing blast furnace slag with carbon, so that TiO2 in the slag is converted into low-valence titanium; the smelting temperature of the three-phase AC closed electric furnace is controlled at 1420℃, the slag discharge temperature is 1600℃, and the smelting time is 60min.

[0031] The carbonaceous reducing agent is formulated at 4.5% of the mass of titanium-containing blast furnace slag, with a particle size of 1-5 mm and a fixed carbon content of 85%.

[0032] ② Using nitrogen as the carrier gas for carbonaceous reducing agent, the slag containing low-valent titanium obtained in step ① is subjected to counter-current blowing and air quenching to obtain titanium carbonitride particles. The nitrogen pressure is controlled at 0.7 MPa, and the nitrogen flow rate is controlled at 120 m / s. During air quenching, the carbonaceous reducing agent ratio is 11% of the mass of the titanium-containing blast furnace slag, with a particle size of 200 μm and a fixed carbon content of 93%. By adjusting the nitrogen flow rate, the hot molten slag containing Ti(C,N) is ensured to form uniformly sized particles with a particle size distribution of 1–2 mm.

[0033] The titanium carbonitride prepared in Example 2 had a grade of 14.75%, the reaction time was shortened by 27 min, and the smelting power consumption was reduced by 16.58%; the water-quenched slag particles were uniform, with 96% being 1-2 mm.

[0034] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing titanium carbonitride from titanium-containing blast furnace slag, characterized in that, The method includes the following steps: ① Use a three-phase AC closed electric furnace with carbon to smelt titanium-containing blast furnace slag, so that TiO2 in the slag is converted into low-valent titanium; ②Using nitrogen as a carrier gas for carbonaceous reducing agent, the slag containing low-valent titanium obtained in step ① is subjected to counter-current blowing and air quenching to obtain titanium carbonitride particles. Step ① The smelting temperature of the three-phase AC closed electric furnace is controlled at 1100℃~1500℃, the slag discharge temperature is 1300℃~1700℃, and the smelting time is 45~60min. Step ① The carbonaceous reducing agent required for carbon preparation is 3.5%~4.5% of the mass of titanium-containing blast furnace slag; Step ② The carbonaceous reducing agent is prepared at a ratio of 9% to 11% of the mass of titanium-containing blast furnace slag.

2. The method according to claim 1, characterized in that, Step ① The particle size of the carbonaceous reducing agent required for carbon preparation is 1~5mm, and the fixed carbon content is ≥75%.

3. The method according to claim 1, characterized in that, Step ② The nitrogen pressure is controlled at 0.4~0.7MPa, and the nitrogen flow rate is controlled at 90~120m / s.

4. The method according to claim 1, characterized in that, Step ② The particle size of the carbonaceous reducing agent is 75~200μm, and the fixed carbon content is ≥90%.

5. The method according to claim 1, characterized in that, Step ② yields titanium carbonitride particles with a particle size of 1~2 mm.

Images